In a Swiss lever escapement, the escape wheel interacts with the pallet-lever with the aid of a mechanical contact force, which generates significant friction and reduces the efficiency of the escapement.
EP Patent Application 13199427 in the name of THE SWATCH GROUP RESEARCH & DEVELOPMENT Ltd discloses the replacement of this mechanical interaction with contactless forces of magnetic or electrostatic origin, which, amongst other things, minimises losses through friction.
The practical embodiment of a magnetic lever escapement requires the interaction energy to be varied using ramps and barriers, as described in the above document.
As regards the magnetic interaction between wheel sets, the prior art mentions the use of discrete magnets interacting with other discrete magnets, such as, for example, in U.S. Pat. No. 3,183,426, or discrete magnets interacting with an iron structure as in FR Patent 2075383 and GB Patent 671360. The use of iron is justified by its ease of machining, which makes it possible to produce small structures that are regularly repeated over the circumference of a wheel. However, magnet-magnet interaction is preferred when the escape wheel moves in jerks, since the energy required to stop the wheel is greater than for continuous systems. Moreover, the use of discrete magnets does not easily allow energy to be continuously varied, in a gentle and linear manner, to produce ramps in an optimum manner as described in the aforecited EP Patent Application 13199427.